About Yeast Pitch Rate
This is a calculator to estimate the amount of yeast you will need to pitch into the wort. If you usually make low- or mid-strength ales and are planning to make a stronger ale or do a cold fermentation (i.e. lager), you need to ensure you have enough yeast to pitch. You can sometimes get away with underpitching or overpitching, but if you want to make exceptional beer, it’s best not to take an easily avoidable risk. After all, Brewers make wort, but Yeast make beer.
Base Yeast Pitch Rate
Recommended amounts of yeast to pitch vary. For example, according to the Institute of Brewing and Distilling (IBD) in the UK, typical pitching rates are the following:
- Lager 15 – 20 million cells / millilitre
- Ales 5 – 15 million cells / millilitre
This equates to:
- Lager 15-20 billion cells / litre (or 57-76 billion cells / US Gallon)
- Ales 5-15 billion cells / litre (or 19-57 billion cells / US Gallon)
Without knowing the gravity of the wort or the health of the yeast, this is a reasonable, albeit large range to go by for most ales and lighter lagers.
A more specific and commonly used pitching rate is 1 million cells / millilitre / degree Plato. This rate has the built-in assumption that the yeast is re-used and therefore is not a concentration of peak performing yeast. When pitching a fresh packet of yeast or a starter, the yeast are quite healthy, so 0.5 million cells / millilitre / degree Plato is a more appropriate estimate of base pitch rate.
Tweaking Pitch Rate for Style
The 0.5 million cells / millilitre / degree Plato pitch rate is an excellent guide if you are making an Ale which is intended to have noticeable esters from the yeast. However, if you intend to make an ale that is “clean” from esters, your pitch rate should be increased. In general, the more yeast you pitch, the less yeast by-products you’ll notice in your beer.
Also, if you are fermenting cold, you will need a higher pitching rate due to the yeasts metabolism working slower due to the lower temperature. Cold fermentations (i.e. lagers) will also take more time.
Underpitching and Overpitching
If you are under the recommended pitching rate, you will have to either: (1) use more packets of yeast, (2) make a starter to propagate more yeast, or (3) take your chances.
If you are over the recommended pitching rate, your fermentation may take-off like a rocket. As long as you’re not intending to make a beer that has noticeable esters or full mouthfeel, this will very likely not be a problem.
In this calculator, a pitch rate is given for for warm or cold fermentations with a desired high, balanced or clean fermentation character. All beers are different, so please consider this as a guide.